L3 cache may refer to any of the following:
1. L3 cache is cache memory located on the die of the CPU. The picture of the Intel Core i7-3960X processor die is an example of a processor chip containing six CPU cores and shared L3 cache. As depicted, the L3 cache is shared between all CPU cores and is very large in comparison to what an L1 or L2 cache would be on the same chip because it is less expensive, albeit slower.
2. L3 is the name of a supplier of surveillance devices, secure communications systems, and navigation products.